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A butterfly diagram of the latitude of sunspot occurrence versus time.
Click on image for full size NASA's Marshall Space Flight Center

Maunder's Butterfly Diagram

Throughout the solar_cycle,
the latitude of sunspot
occurrence varies with an interesting pattern.
The plot on the left shows the latitude of sunspot occurence versus
time (in years).
Sunspots are typically confined to an equatorial belt
between -35 degrees south and +35 degrees north latitude.
At the beginning of a new solar cycle, sunspots tend to form at
high latitudes, but as the cycle reaches a maximum (large numbers
of sunspots) the spots form at lower latitudes. Near the
minimum of the cycle, sunspots appear even closer to the equator,
and as a new cycle starts again, sunspots again appear at
high latitudes. This recurrent behavior of sunspots gives
rise to the ``butterfly'' pattern shown, and was first
discovered by Edward Maunder in 1904. The reason for this
sunspot migration pattern is unknown. Understanding this pattern
could tell us something about how the Sun's internal magnetic
field is generated.

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